COMMUNICATION SYSTEM AND COMMUNICATION TERMINAL

• US 20120228927A1
• Filed: 07/28/2010
• Published: 09/13/2012
• Est. Priority Date: 07/28/2009
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Matsumoto, Tadashi, Koise, Shoji
• Granted Patent: US 9,509,530 B2
• Time in Patent Office: Days
• US Class Current: 307/3
• CPC Class Codes: H04B 2203/547 via DC power distribution
• CPC Class Codes: H04B 3/548 the power on the line being DC arrangements for feeding power H04L12/10; extracting feeding power from signals H04L25/02
• CPC Class Codes: H04L 25/0278 Arrangements for impedance matching
• CPC Class Codes: H04L 25/0294 Provision for current-mode coupling

Abstract

A transmitting circuit is connected to a communication line and configured to transmit a primary signal, being a current signal, to the communication line by changing a current flowing from a transmission unit via the communication line. A receiving circuit is configured to receive a secondary signal which is generated by converting the primary signal transmitted from the transmitting circuit to a voltage signal by a current/voltage converter provided between the transmission unit and the communication line. Specifically, the primary signal, being a current signal transmitted from a communication terminal, is converted to the secondary signal being a voltage signal by the current/voltage converter. As a result, communication can be performed even when the impedance of the communication line is reduced, facilitating introduction of a communication system.

Claims

1. A communication system comprising:

a plurality of communication terminals connected to a two-wire communication line;

a power supply device configured to apply voltage between two wires of the communication line; and

a current/voltage converter configured to convert change of current on the communication line to change of voltage on the communication line by a voltage drop by a resistance component,

the communication terminals each including;

a transmitting circuit connected to the communication line and configured to generate a primary signal, being a current signal, on the communication line by changing a current flowing from the communication line; and

a receiving circuit configured to receive a secondary signal which is generated by converting the primary signal to a voltage signal by the current/voltage converter.

2. The communication system according to claim 1, wherein characteristic impedance of the communication line is utilized as the resistance component by the current/voltage converter.

3. The communication system according to claim 1, wherein a resistance element connected between the power supply device and the communication line is utilized as the resistance component by the current/voltage converter.

4. The communication system according to claim 1, wherein an inductance element connected between the power supply device and the communication line is utilized as the resistance component by the current/voltage converter.

5. The communication system according claim 1, wherein the receiving circuit receives, as the secondary signal, the change of voltage which is generated on the communication line due to voltage drop when the current flowing from the communication line is changed by the transmitting circuit.

6. The communication system according to claim 1, wherein the power supply device includes a signal transmitting section that transmits a first protocol signal, being a voltage signal, to the communication line by changing a magnitude of a voltage applied to the communication line, and the receiving circuit receives, as the secondary signal, a secondary protocol signal having a higher frequency than a frequency of the first protocol signal and superimposed on the first protocol signal.

7. The communication system according to claim 1, wherein the receiving circuit includes a comparator circuit that extracts a signal component of the secondary signal by binarizing the secondary signal by comparing the magnitude of the secondary signal with a predetermined threshold value, and when transmitting the primary signal from the transmitting circuit, the communication terminal sets input impedance viewed from the communication line to be low to suppress an amplitude of the secondary signal so that a component excluding the signal component of the secondary signal does not exceed the threshold value.

8. The communication system according to claim 1, wherein the receiving circuit includes an amplifier circuit configured to perform conversion to change of voltage from a first reference voltage by amplifying the secondary signal;

and a comparator circuit configured to binarize the secondary signal by comparing an output of the amplifier circuit with a secondary reference voltage, the first reference voltage being set to be deviated from the second reference voltage.

9. The communication system according to claim 1, wherein the receiving circuit includes a comparator circuit configured to binarize the secondary signal by comparing a magnitude of the secondary signal with a predetermined threshold value;

and a correction circuit configured to detect rising or falling of the secondary signal as a trigger, and correct the secondary signal to a square wave having a predetermined pulse width from a detection point of the trigger.

10. The communication system according to claim 9, wherein the transmitting circuit includes an encoding section configured to encode transmission data such that a value not allowing the trigger to be generated is not continued in the secondary signal, and the receiving circuit includes a decoding section configured to decode the encoded data obtained from the secondary signal to acquire the transmission data.

11. A communication terminal used in a communication system that includes a power supply device configured to apply voltage between two wires of a communication line, and a current/voltage converter configured to convert change of current on the communication line to change of voltage on the communication line by a voltage drop by a resistance component,

the communication terminal comprising:

a transmitting circuit connected to the communication line and configured to transmit a primary signal, being a current signal, to the communication line by changing a current flowing from the communication line; and

a receiving circuit configured to receive a secondary signal which is generated by converting the primary signal to a voltage signal by the current/voltage converter.